This invention relates to an inflatable life raft having inflatable tubes dimensioned and positioned to cause the life raft to turn upright in the water without assistance if the raft inflates in an inverted position or to return an inflated raft to an upright position if it is subsequently overturned.
In U.S. Pat. No. 4,998,900, there is described and illustrated a self-righting inflatable life raft having upwardly and outwardly extending inflatable tubes. These tubes are arranged to cause the life raft to be unstable if inverted. In particular, the centre of gravity of an inverted life raft will fall outside the supporting area, that is the top of the inflatable tubes, so that the life raft will topple under gravity back to an upright position.
If the inflatable tubes in these prior constructions do not inflate or, after inflation are subsequently collapsed or distorted, they may not adopt their desired positions extending upwardly and outwardly from the side of the walls of the main body, sufficient to make the life raft topple to the upright position.
In patent application PCT/AU96/00409 similar self-righting inflatable life rafts were disclosed incorporating ties in the form of flexible ropes, wires or inflatable tubes fixed between two spaced points on the life raft to limit separation of the two points to the length of the tie during and after inflation of the tube members. The two points were chosen to inhibit distortion or collapse of the tube members from their desired positions when inflated.
It is an object of the present invention to provide a life raft which can reliably return to an upright position if inverted.
According to the present invention there is provided a self-righting inflatable life raft comprising a raft body having inflatable side walls and a floor located therebetween; and at least two inflatable tube members forming arches that extend from one side of the raft body to the other, each arch extending upwardly and outwardly from a perimeter of said raft body at an angle from the perpendicular to said raft body; said life raft having a central axis and a centre of gravity through which the weight of the life raft acts to rotate the raft on the surface of water from an unstable inverted position to a stable upright position, wherein the tube members have a buoyancy sufficient to exert a turning moment on said life raft causing said life raft to topple by gravity to an upright position, characterised in that at least one inflatable interconnecting tube is positioned between the arches and offset from a central axis to increase the turning moment.